Switch to an iterator for traverse_nodes.
Switch to an iterator for traverse_nodes.

We can't use a slice anymore, because the input might be the VecDeque from the
sequential traversal, which requires an iterator to handle the ring buffer.

MozReview-Commit-ID: JwH6MtRgMfY

KiChjang/servo,sadmansk/servo,KiChjang/servo,notriddle/servo,paulrouget/servo,avadacatavra/servo,KiChjang/servo,upsuper/servo,jimberlage/servo,mattnenterprise/servo,KiChjang/servo,CJ8664/servo,eddyb/servo,DominoTree/servo,jimberlage/servo,emilio/servo,CJ8664/servo,KiChjang/servo,larsbergstrom/servo,SimonSapin/servo,avadacatavra/servo,DominoTree/servo,fiji-flo/servo,KiChjang/servo,pyfisch/servo,SimonSapin/servo,KiChjang/servo,peterjoel/servo,notriddle/servo,thiagopnts/servo,saneyuki/servo,anthgur/servo,SimonSapin/servo,notriddle/servo,thiagopnts/servo,rnestler/servo,peterjoel/servo,DominoTree/servo,splav/servo,avadacatavra/servo,pyfisch/servo,SimonSapin/servo,paulrouget/servo,splav/servo,thiagopnts/servo,ConnorGBrewster/servo,paulrouget/servo,eddyb/servo,thiagopnts/servo,notriddle/servo,pyfisch/servo,emilio/servo,notriddle/servo,nnethercote/servo,upsuper/servo,sadmansk/servo,szeged/servo,larsbergstrom/servo,avadacatavra/servo,szeged/servo,anthgur/servo,szeged/servo,fiji-flo/servo,peterjoel/servo,paulrouget/servo,jimberlage/servo,saneyuki/servo,ConnorGBrewster/servo,KiChjang/servo,dsandeephegde/servo,mbrubeck/servo,upsuper/servo,sadmansk/servo,DominoTree/servo,thiagopnts/servo,jimberlage/servo,anthgur/servo,cbrewster/servo,saneyuki/servo,emilio/servo,nnethercote/servo,dati91/servo,rnestler/servo,mattnenterprise/servo,szeged/servo,thiagopnts/servo,fiji-flo/servo,fiji-flo/servo,pyfisch/servo,emilio/servo,avadacatavra/servo,nnethercote/servo,dsandeephegde/servo,canaltinova/servo,jimberlage/servo,mbrubeck/servo,saneyuki/servo,rnestler/servo,emilio/servo,splav/servo,rnestler/servo,cbrewster/servo,upsuper/servo,larsbergstrom/servo,nnethercote/servo,canaltinova/servo,mattnenterprise/servo,upsuper/servo,anthgur/servo,szeged/servo,splav/servo,cbrewster/servo,cbrewster/servo,anthgur/servo,eddyb/servo,dati91/servo,szeged/servo,emilio/servo,rnestler/servo,notriddle/servo,pyfisch/servo,eddyb/servo,dati91/servo,DominoTree/servo,dsandeephegde/servo,mattnenterprise/servo,dati91/servo,nnethercote/servo,ConnorGBrewster/servo,mbrubeck/servo,mbrubeck/servo,pyfisch/servo,mattnenterprise/servo,dsandeephegde/servo,cbrewster/servo,splav/servo,paulrouget/servo,ConnorGBrewster/servo,emilio/servo,fiji-flo/servo,SimonSapin/servo,DominoTree/servo,saneyuki/servo,CJ8664/servo,CJ8664/servo,szeged/servo,saneyuki/servo,peterjoel/servo,larsbergstrom/servo,ConnorGBrewster/servo,SimonSapin/servo,thiagopnts/servo,splav/servo,emilio/servo,ConnorGBrewster/servo,peterjoel/servo,szeged/servo,canaltinova/servo,fiji-flo/servo,eddyb/servo,upsuper/servo,mbrubeck/servo,jimberlage/servo,eddyb/servo,peterjoel/servo,eddyb/servo,nnethercote/servo,saneyuki/servo,peterjoel/servo,pyfisch/servo,larsbergstrom/servo,upsuper/servo,DominoTree/servo,szeged/servo,SimonSapin/servo,nnethercote/servo,CJ8664/servo,dati91/servo,mattnenterprise/servo,larsbergstrom/servo,notriddle/servo,peterjoel/servo,cbrewster/servo,notriddle/servo,paulrouget/servo,splav/servo,emilio/servo,fiji-flo/servo,anthgur/servo,canaltinova/servo,KiChjang/servo,peterjoel/servo,larsbergstrom/servo,CJ8664/servo,DominoTree/servo,anthgur/servo,saneyuki/servo,mbrubeck/servo,sadmansk/servo,paulrouget/servo,rnestler/servo,mattnenterprise/servo,fiji-flo/servo,peterjoel/servo,mbrubeck/servo,dati91/servo,SimonSapin/servo,jimberlage/servo,paulrouget/servo,szeged/servo,avadacatavra/servo,upsuper/servo,DominoTree/servo,avadacatavra/servo,canaltinova/servo,sadmansk/servo,canaltinova/servo,nnethercote/servo,sadmansk/servo,larsbergstrom/servo,dsandeephegde/servo,CJ8664/servo,paulrouget/servo,thiagopnts/servo,jimberlage/servo,dsandeephegde/servo,larsbergstrom/servo,nnethercote/servo,anthgur/servo,larsbergstrom/servo,ConnorGBrewster/servo,emilio/servo,splav/servo,ConnorGBrewster/servo,paulrouget/servo,notriddle/servo,saneyuki/servo,pyfisch/servo,nnethercote/servo,splav/servo,canaltinova/servo,saneyuki/servo,pyfisch/servo,CJ8664/servo,KiChjang/servo,notriddle/servo,rnestler/servo,cbrewster/servo,avadacatavra/servo,eddyb/servo,DominoTree/servo,rnestler/servo,sadmansk/servo,jimberlage/servo,mbrubeck/servo,canaltinova/servo,sadmansk/servo,pyfisch/servo,splav/servo,mattnenterprise/servo,cbrewster/servo,dati91/servo,dsandeephegde/servo,dsandeephegde/servo,dati91/servo